To follow up, what's with the ridiculous posture associated with old timely boxing matches?

You're right, the modern conception of a fist fight is heavily influenced by the modern sport of boxing. The biggest change is the use of boxing gloves, which seem to have been first mandated in the "Queensbury Rules" from Britain in the 1860's. Before that, bareknuckle boxing matches were common. If you go back to ancient times, it seems to indicate that leather strips worn about the knuckles were utilized. But there isn't much difference between bareknuckle and wearing thing leather wrappings- the leather would mainly serve to protect your fist from being cut; they don't have enough protection to prevent your hand from being broken, like a modern 12-16oz boxing gloves does.

A boxing glove distributes the force of the punch over a much large area of the hand- basically from the second knuckle of the fingers to the first, and everything in between. This makes a big difference because knuckles are pointy and irregular and can easily break when you throw a punch bareknuckled against a hard surface, like someone's face. Basically, boxing gloves let you punch a lot harder without breaking your hands. Boxing gloves do NOT offer much protection to the person being punched, except against superficial cuts to the face. They primarily protect the hands of the puncher.

What this means is that before the modern boxing era, punches were not as hard. You saw a lot more body punches because the body presents a more appealing target than the skull to hit with a bare hand. Face shots are more likely to be aimed at the chin or nose than the temples. Not unlike the striking scene in modern MMA. Knockouts are less frequent- you would get knockDOWNS from a well struck blow, but lacking the necessary force to send the brain careening into the skull, the fighter would quickly regain his senses.

I've done some research on ancient Greek boxing which was an Olympic sport, as well as Pankration which was like modern MMA, a combination of boxing and wrestling. There is precious little information to be found, unfortunately.

One of the really awesome passages that does exist comes from Pausanias, describing a Pankration contest:

"For when he was contending for the wild olive with the last remaining competitor, whoever he was, the latter got a grip first, and held Arrhachion, hugging him with his legs, and at the same time he squeezed his neck with his hands. Arrhachion dislocated his opponent's toe, but expired owing to suffocation; but he who suffocated Arrhachion was forced to give in at the same time because of the pain in his toe. The Eleans crowned and proclaimed victor the corpse of Arrhachion."

Paus. 8.40.2 http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.01.0160%3Abook%3D8%3Achapter%3D40%3Asection%3D2

I realize I have shifted to touching on the grappling/wrestling aspect more than the punching... but the fact of the matter is that most people think that "fistfights" play out like a modern sport boxing match and that isn't the case. It usually involves a lot more grabbing and shoving in between short punches thrown to the body and softer parts of the heads. Given that an ancient society like the archaic Greeks or Rome under the Republic expected males to be able to fight in a war, it makes sense that even unarmed combat would probably be skewed towards techniques that are more useful on the battlefield. No one has ever boxed on a battlefield. You grab and pull and fight for leverage until you can stab your opponent.'

Edit:

See Paus. 8.40.3 for commentary on the gloves used in competition.

Edit 2:

Does anyone have information on the invention/development of the jab? I used to have an interesting source on this but cannot find it.

We actually know a fair bit about ancient boxing. I apologize, my book on ancient sports is on campus. However, we do have several accounts and lots of images of ancient boxing.

There are boxing matches in both the Iliad and the Odyssey. The account in the Iliad is more impressionistic, but in the Odyssey (and I have read this in Greek), it sounds like a pretty technical description:

Irus hurled a fist at Odysseus' right shoulder as he himself came through with a hook below the ear, pounding Irus' neck, smashing the bones inside (here's the Greek - the hook could be Fagles' embellishment δὴ τότ᾽ ἀνασχομένω ὁ μὲν ἤλασε δεξιὸν ὦμον Ἶρος, ὁ δ᾽ αὐχέν᾽ ἔλασσεν ὑπ᾽ οὔατος, ὀστέα δ᾽ εἴσω ἔθλασεν).

Boxing remained a topic of poetry, occurring in Theocritus, The Argonautica, and the Aeneid.

As for pictures: we have [sculptures] (http://upload.wikimedia.org/wikipedia/commons/b/bb/Thermae_boxer_Massimo_Inv1055.jpg) (there are little Roman models that I couldn't find tonight EDIT: Found one!), and vase paintings ([1]http://ancientolympics.arts.kuleuven.be/picEN/slides/P0011.jpg) , 2), and wall paintings.

To my mind, the images don't seem completely foreign. I think I know what I'm looking at, same for the literary descriptions. We do know the rules were different - They seem to have been much more constrained; the ref would push the fighters together rather than apart, and there's at least one story of a fight going into "overtime" in which each fighter traded one punch at a time in a "sudden death" mode.

I'm sorry my book is on campus. I've given a link if you want to look it up yourself or I can follow up some unspecified time in the future.

To follow up: is that true that fist-fighting used to be a "Euro" thing and for example Middle Easterners used to fight - in a random street fight without rules - with slaps, not punches?